What is Silicon Controlled Rectifier? SCR

SCR is a 4 layer 3 junction and three terminal devices is shown below the and pain reason is the anode and the end reason is the cathode and the enemy reason is the gate the anode to cathode is collected in the series with the load circuit essentially the device is a switch ideally positive voltage with respect to the cathedral there then switch on the current flows and continuous to conduct without for the gate signal ideally the SCR has zero impedance in conduction state for switching off or reverting to the blocking state there must be no get current and the anode current must be reduced to zero current can flow only in One Direction nausea of voltage rating 10kv and RMS current rating of 35000 amperes with speed of 1 ms corresponding to a power handling capacity of 30 megawatt are available in it can be faced by a low voltage supply of about one ampere and 10 watt

obviously it has tremendous power amplification because of its compactness high reliability and low loss the CR has almost replace the earlier power switching device thyratron and the magnetic amplifier as mentioned above this year is a four layer device with three terminals namely the anode and cathode in the gate when the anode is made positive with respect to the cathode junction J1 and J2 hard for Roadways and Junction to is Reverse bias and only the leakage current will flow through the device that air is then said to be in the forward blocking state or in the forward more or of state but when the cathode is made poster with respect to the inauguration J1 J2 are reverse bias a small rivers leakage current will flow through the SCR and SCR is said to be the reverse blocking state or in Reverse mode

when the anode is positive with respect to CAD for when the SCR is informed IMO this year does not conduct unless the forward voltage exceeds certain value called the forward breakover voltage in conducting state the current through this year is the leakage current which is very small and is knowledgeable if a positive get current is supplied the CR can become conducting auto voltage must lesser than forward breakover voltage the larger the gate current lower The breakdown voltage current the CRV has identical to PN rectifier once the SCR is switched on the forward voltage drop across it suddenly reduced very small value about 1 volt in the conducting or on state the current through the SCR is limited by the external impedance when the anode is negative with respect to cathode when the SCR is in Reverse mode or unblocking state no current flows Valencia accept very small leakage current of the order of few microamperes but if the reverse voltage is increased beyond a certain value called the rivers breakover voltage Avalanche breakdown takes place for trip over voltage is usually higher than rivers spread over voltage from the following discussion it can be seen that the share has to stable and reversible operating state that changed over the voltage from of state to on state called turn on can be achieved by increasing the forward voltage beyond VPO a more convenient and useful method of turning on device employee The Great Red the foreign bodies is lesser than the forward breakover voltage it can be done by the up like a boss 12 current the great and the cat food the method is called the gate control another very important feature of the rate is that one day she has triggered to on state the gate loses its control

the applied voltage there is however small current about potential drop across the SCR the forward current through the SCR can be reduced by reducing the applied voltage or by increasing the circuit impedance there is however a minimum forward current that must be maintained to keep the CR in conducting state there is called the holding current rating of SCR if the current through the cell is reduced below the level of holding current the device return to of state of locking state there can be switched off by reducing The Hobbit current below the level of holding current which may be termed as as a reducing the applied voltage or by decreasing the current speed internet services of by blood negative voltage to the inert gas manually while switched off year one point is not worthy DesiJatt Ek certain time to switch off the time at the turn of time must be allowed before forward voltage may be applied again otherwise the device will switched on forward voltage without any Great Falls does turn off time is about to 15 microsecond which is immaterial when dealing with powerful can see but they become important in the inverter circuit which are to operate at high frequency there are mainly to type of SCR for using motor controlled in water grid and converter grade for the ones are used in inverters cycloconverters and brushless DC motor system while the letter is used in the chopper phase controlled rectifier IC regulator it is there the two braids vary in their timely response in water state grid SCR are costlier than the converter grade

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